The primary aims of this research are: 1. The exploration in a close collaborative and cooperative manner of those areas of biology which are relevant to mental retardation. 2. To conduct basic investigations into the etiology, pathogenesis, and prevention of mental retardation, utilizing biomedical techniques. 3. To provide the milieu for training of young scientists with similar interests and increasing competence. A group of scientists primarily interested in biological or biomedical approaches to mental retardation has been assembled to form this program project. The direction of the investigation is via a time scale which includes the prenatal, perinatal, and postnatal periods and continues through adolescence to young adulthood. The investigators' interests and experiences also include collaboration with behavioral scientists and an increasing interest in the earliest phases of pregnancy including preconception. Several different levels of study will be undertaken--genetic, biochemical, physiological, behavioral, biostructural, biomathematical and clinical.